1993 AK Karst Panel

128 Pages·2006·1.06 MB·English

by  William R. Elliott

KARST AND CAVE RESOURCE SIGNIFICANCE ASSESSMENT
KETCHIKAN AREA, TONGASS NATIONAL FOREST, ALASKA.

November 23, 1993

Report of the Karst Resources Panel

Thomas Aley, Panel Leader
Ozark Underground Laboratory, Protem, MO.
Catherine Aley, Panel Member
Ozark Underground Laboratory, Protem, MO.
William R. Elliott, PhD., Panel Member
Research Fellow, Texas Memorial Museum, Univ. of
Texas, Austin, TX.
Peter W. Huntoon, PhD., Panel Member
Professor of Geology, Univ. of Wyoming, Laramie, WY

A study and report prepared by the Ozark Underground
Laboratory under contract to Ketchikan Area, Tongass
National Forest, Federal Building, Ketchikan, Alaska
99901.

[This report is a slightly reformatted facsimile of
the original.]

Educational Field Programs (cid:121) Water and Land Use Investigations in Soluble Rock Terrains (cid:121) Research Facilities and Assistance
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EXECUTIVE SUMMARY
Karst is a three dimensional terrane developed on, and
within, a soluble bedrock. At least 700 square miles of
the Ketchikan Area of the Tongass National Forest (the
“study area”) is karst, and it is likely that the extent
of karst will prove to be larger when more detailed
geologic mapping is conducted. Karstlands extend from
salt water to some of the peaks. Springs, caves,
sinkholes, losing streams, and a host of other karst
features are abundant and often spectacular.
A Karst Resources Panel (“the Panel”) was established
under contract to the Forest Service to: (1) assess the
significance of the karst, (2) determine the
effectiveness of present strategies for protecting karst
resources and recommend appropriate changes, and (3)
recommend focused resource evaluation goals and research
for karst areas. This report documents the results of
this work.
The climatic, geological, and biological setting of
the study area is fundamental to an adequate
understanding of the significance of its karst resources.
The climate is temperate and maritime. Precipitation is
abundant; it may exceed 250 inches a year at some higher
altitudes; annual runoff ranges from about 60 to 200
inches a year. The carbonate rocks that comprise these
karst areas originated on tropical Pacific islands that
were transported by plate tectonic movements to their
current locations. There is no other place in the world
where tropical limestones have travelled so far, been
involved in such an oblique collision with a continent,
and ended up emplaced in an archipelago setting at such
high latitudes. Finally, karst portions of the study area
are found in temperate coniferous rain forests, adjacent
to peatlands, and in both subalpine and alpine zones.
The diversity of karst resources, features, and cave
types present in the study area exhibit unusual breadth.
Epikarst is an intensely dissolved veneer of intersecting
roofless dissolution-widened fissures, cavities, and
tubes dissolved into the surface of the carbonate
bedrock. Typical thicknesses of the epikarst zone range
from more than 100 feet in recently unglaciated alpine
areas to
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less than 5 feet in recently glaciated low elevation
areas. The quality of some of the epikarst in the study
area is surpassed only by selected tropical epikarsts in
places such as China, Papua New Guinea, and Madagascar;
certainly there is no better epikarst in the United
States.
Vertical shafts and caves are abundant. Some areas
have sinkhole densities estimated at 3,000 to 10,000 per
square mile. The caves are highly diverse in form and
age. Some of them are of great antiquity. Other are
intimately associated with up-gradient peatlands. Por-
tions of the area contain superb littoral (sea) caves,
some of which were formed when massive weights of glacial
ice had depressed the land surface relative to sea level.
A troglobitic amphipod, Stygobromus quatsinensis, was
discovered on Heceta Island (55°45’53”N) during the
Panel’s visit. This discovery is a high-latitude Western
Hemisphere record for a cave—adapted species.
Archeological and paleontological deposits in the area
are primarily known from cave and rockshelter sites.
Preservation of bone and organic materials is excep-
tionally good in these cold environments. To date,
significant archeological and paleontological materials
have been discovered in at least thirty caves and rock—
shelters on seven islands in the study area. Such
material is of international importance in tracing the
regional prehistory, the effects of climatic changes, and
the colonization of the Alexander Archipelago by wildlife
and humans at different times in the past.
The karstlands of the study area, and the caves
within, have enormous recreational values. They offer
beauty, discovery, and adventure. The entire Panel was
extremely impressed by the exceptional recreational
values existing in the karst of the area.
It is the conclusion of the Panel that karst resources
of the study area possess eight attributes which are of
international-scale significance. These are:
1. The occurrence of major karst development in the
unique geologic and archipelago setting of Southeast
Alaska.
2. The occurrence of significant portions of the
karst in a largely undisturbed, high-latitude temperate
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coniferous rain forest. Such settings are, for practical
purposes, globally limited to Southeast Alaska. Small
amounts of karst in temperate coniferous rain forest
remain on Vancouver and Queen Charlotte Islands.
3. The tremendous diversity of karst features present
in the study area.
4. The quality of natural preservation of karst
resources.
5. The density and degree of development of karst
features.
6. The existence of large and extremely well—preserved
littoral (sea) caves, some of which are now located at
elevations higher than present—day sea level.
7. The presence and abundance of archeological
resources which include cave art and may include
critically important deposits helping us understand
prehistoric colonization of the North American Continent.
8. The existence of outstanding and unique paleon—
tological deposits of international significance in
understanding climatic changes and their effects.
The panel further concludes that karst resources of
the study area possess nine attributes of national—scale
significance. These are:
1. Regional karst dissolution rates (regional
denudation rates) on the order of at least 4 to 8 times
greater than rates in most other American karst areas.
2. Abundant and unique moonmilk deposits.
3. Intimate relationship between peatlands and
vertical shaft development in adjacent down—slope car-
bonate rocks.
4. Contribution of runoff water to some of the
most significant fisheries streams in the study area; it
is probable that streams draining karst areas have appre-
ciably greater aquatic productivity than streams draining
nonkarst areas. The fisheries resources of streams in the
study area are clearly of national significance.
5. Troglobitic (cave—adapted) invertebrates on inner
islands (such as Prince of Wales) are either very rare or
absent; such species are found on outer islands (such as
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Heceta and Dali). This difference is probably
attributable to differences in the extent of recent
glaciation.
6. Discovery of a troglobitic cave amphipod, Sty-
gobromus quatsinensis, in a cave on Heceta Island.
7. Cave use by large mammals to an extent no longer
seen in the “Lower 48 States”.
8. The unique opportunity to study evolution and
adaptation of invertebrates in an archipelago setting
with a complex geologic and glacial history.
9. The recreational potential of vast and largely
untouched and unexplored caves and cave passages beneath
“the last frontier” of Alaska.
Karst systems impose major land management liabilities
not encountered in nonkarst areas. The subsurface karst
drainage networks generally operate independently of, and
with more complexity than, the surface drainage systems
above them. Three important considerations apply. First,
the size and shape of the karst systems often have little
or no relationship to the overlying surface drainage
systems. Second, the direction of flow through the karst
systems often cannot be predicted from surface topography
or geologic mapping. Third, the discharge from a karstic
groundwater system is not always localized at one spot as
occurs in a surface drainage basin. Water entering one
sinkhole in a basin may discharge from several springs at
diverse compass bearings from the input sinkhole. Flow
velocities in the groundwater system often equal or
approach surface stream velocities. Pollutants such as
diesel fuels or fine sediments from roads or other dis-
turbed lands can arrive unexpectedly at one or more
distant springs within hours to a few days. Human water
supplies and fisheries are routinely, and severely,
impacted by such events in karst areas.
In nonkarst portions of the study area sediment must
move laterally to a stream, and then flow down the
stream. Management efforts are made to protect riparian
corridors from logging and its impacts. The large amounts
of slash and cull materials remaining on the ground after
logging, plus the heavy moss growths on the ground prior
to logging, help trap and retain substantial amounts of
the sediment. Vegetation can rapidly become established
on trapped sediments.
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Karst areas transport sediment differently from
nonkarst areas. In karst, much of the sediment must move
laterally for only a few feet before it is directly
transported downward into conduit portions of the karst
groundwater system. Once sediment is in the conduits
there are no effective natural processes for trapping and
retaining it within the system; as a result, it is
delivered to a receiving spring or stream. As
demonstrated by the dye—tracing work conducted by the
Panel, the receiving spring or stream may be several
thousand feet away from the point of sediment
introduction.
Areas with deep and well—developed epikarst have more
closely spaced near—surface openings into which sediments
can be flushed than is the case in areas with only
shallow epikarst. As a result, sediment transport
potential is typically much greater in areas underlain by
deep and well-developed epikarst. Observations by this
Panel indicate that most of the thin epikarst occurs in
areas at relatively low elevations on the inner islands.
These are also areas with typically less rugged relief.
Much of the remaining virgin forest on karst is underlain
by deep and well-developed epikarst and is characterized
by steeper slopes. When timber harvest and road
construction occur on well—developed epikarst with steep
slopes, sediment transport and erosion problems will be
substantially greater than on the thin epikarst and lower
relief lands.
The importance of cave resources has been recognized
by the Forest Service in the study area since 1988. This
recognition, and the enactment of the Federal Cave
Resources Protection Act in 1988, led to cave inventory
work and ultimately to the development of standards and
guidelines. These contain laudable features and in some
cases provide adequate protection for cave features.
Cases where adequate cave protection occurs typically
have both of the following characteristics:
1. The block of forest in which the cave entrance is
located has not been logged or roaded and the cave is far
enough from clearcut areas that accelerated windthrow of
trees does not reach to areas close enough to the cave
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entrance to alter entrance microclimate.
2. None of the area which contributes water to the
cave is affected by logging or road construction.
Cases where implementation of the existing standards
and guidelines has not provided adequate protection for
cave features typically have some or all of the following
characteristics:
1. The area around the cave entrance has been logged
and no buffer zone, or else only a narrow buffer zone, of
uncut trees was left around the entrance. Windthrow of
trees, when they are left in small, isolated patches, is
excessive and appears to almost always occur.
2. Roads, quarries, or clearcuts were located in areas
which contribute waters to the cave.
3. Caves were not discovered early enough to modify
the cutting area and/or road construction.
We have identified six short comings of present cave
resource protection actions in the study area. They are:
1. The level of effort expended in reconnaissance work
to locate and assess caves has been inadequate. This is
to be expected in a fairly new program.
2. Insufficient time between reconnaissance work to
locate and assess caves and the start of road
construction or timber harvest activities. This results
in last minute surprises and band—aid—mitigation efforts
instead of sound resource management.
3. Inadequate recognition of the adverse impacts of
roads on cave resources.
4. Inadequate recognition of the adverse impacts of
quarries on cave resources.
5. Typical cave resource protection in the study area
has focused almost exclusively on those caves reached
through humanly accessible cave entrances. Such humanly
accessible caves are only a fraction of the total cave
resource. There are karst portions of the study area
where surface features clearly demonstrate that caves,
and probably very sizeable caves, underlie the area. Such
caves are not receiving resource management attention
compatible with that provided for caves with open
entrances; this is not a desirable resource management
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situation.
6. Cave resource protection actions have focused upon
cave features (and particularly cave entrances) rather
than upon cave systems. Cave resource protection must
shift its focus from feature protection to system pro-
tection strategies.
A management strategy of recharge area delineation and
vulnerability mapping is recommended by the Panel. The
recharge area for a cave or spring is the area that
contributes water to the cave or spring. In some cases
the recharge area is little more than the land that
overlies the cave. However, in many cases (and especially
when the cave contains streams or lakes) the recharge
area may be very large. Groundwater tracing is a fun-
damental tool for recharge area delineation.
Vulnerability mapping is a land management tool that
has been used effectively in a number of karst areas. It
utilizes the fact that some lands in a karst area create
appreciably greater groundwater contamination risks than
other lands. Recharge area delineation, in concert with
vulnerability mapping, is appropriate and necessary for
sound land management in the karst of the study area.
Such delineation and mapping will help insure that land
use and land management actions in karst portions of the
study area are appropriately tailored to site conditions.
Features and conditions that should be incorporated into
a recharge area delineation and vulnerability mapping
strategy are outlined.
The Panel reached 12 summary conclusions:
1. The karst and caves of the study area have
attributes of international—scale significance.
2. The karst and caves of the study area have
attributes of national—scale significance.
3. Significant karst resources are likely to extend
into other areas of the Tongass National Forest.
4. Karst attributes of national and international
scale significance are being degraded by (1) timber
harvesting, (2) road location, construction, and opera-
tion, and (3) quarry construction and inadequate closure.
5. Resource management in the study area must be
conducted with adequate recognition of the archipelago
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setting of the area and its associated ecosystems.
6. Unique karst-specific conditions require that
management of karstiands must follow a different man-
agement track from the track appropriate to nonkarst
areas. The karst areas should be thought of, and managed,
as islands within islands.
7. The Panel is concerned about reforestation con-
ditions that commonly occur on the karstiands following
timber harvest and that degrade the utility and/or the
utilization of karst resources.
8. Karstiands are of critical importance to the
fisheries of the area. Maintenance of long term high
productivity in these streams will be a major benefit
from improved karstiand management.
9. Cave resource protection actions by the Forest
Service have been laudable, but have commonly not
provided adequate protection for cave features.
10. Management of karstlands should involve four
key components: (A) inventories of karst features, (B)
recharge area delineations, (C) vulnerability mapping,
and (D) incorporation of results from items A through C
into planning and land management decisions.
11. The Forest Service should identify one or two
high-quality, but minimally-impacted, karst areas for
possible designation as a Research Natural Area.
12. Ten future study topics have been identified and
prioritized. Concurrent efforts on multiple items will
probably be superior to placing all effort on a single
item. Top priority should be given to:
A) Protection and study of archeological and paleonto—
logical deposits because they are fragile and irre-
placeable.
B) Testing and implementation of the outlined approach
for recharge area delineations and related vulnerability
mapping.
C) Cave resource inventories and mitigation assessments
should be expanded and enhanced to ultimately insure that
they are reflective of the entire range of karst
resources.
D) Karst resources on other areas of the Tongass National
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Forest are largely unknown and may be of comparable, and
potentially complimentary, significance to those now
known in the Ketchikan Area; they should be assessed.
It is only very recently that the Forest Service has
begun to recognize the significance of karst resources in
the study area. With this ever-growing recognition of
significance has come awareness of resource vulner-
ability. This recognition and awareness led to the work
of this Panel. Our Panel’s conclusions have clearly
demonstrated that the karst resources of the study area
are of tremendous national and international significance
for a substantial number of reasons. We have also dem-
onstrated that many of these unique and priceless
resources are also highly vulnerable to resource damage.
The challenge facing the Forest Service is to integrate
management of karstlands into general land management.
The Forest Service must adequately protect and utilize
the host of newly—recognized resources and resource
interactions; recognizing new resources does not mean
forgetting older resources. The Forest Service goal must
be ecologically sound and scientifically credible
resource management of the karstlands of the study area.
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